Influence of Soil Properties on Arsenic Availability in Soil

The effect of soil properties, namely, texture, soil moisture regime, salinity, available P, Fe, Zn and organic matter content on available arsenic content in soil was investigated in the laboratory incubation studies. The soils used were those from Baruipur and Canning in the district of South 24-Parganas, West Bengal, representing coastal soils (Typic Haplaquept) of the Indo-Gangetic alluvial plains. The Baruipur soil was loam in texture while the Canning soil was a silty clay. Results indicated that the increase in the arsenic availability in soil with rates of added arsenic was more in coarse textured soil than in the fine textured one. The available arsenic (extracted with 0.05 M NaHCO₃, pH 8.5) content of soil increased in presence of added phosphatic fertilizer, organic manure, salinity and under waterlogging, while it decreased with application of Fe and Zn fertilizers as well as on drying of soil. Application of Fe fertilizer appeared to be relatively more effective in reducing arsenic availability in soil. Application of high doses of P fertilizer and organic manure to arsenic contaminated soils should be restricted to avoid enhanced availability of soil arsenic. It appeared that inappropriate management of arsenic affected soils or those irrigated with arsenic contaminated water might increase the arsenic availability in soil, which, in turn, might aggravate the arsenic contamination of crops grown.